(Figs. 2–5)
Etymology. The species name “ puxcu ”, which means ”sister” in the indigenous huarpe language (specifically in the allentiac dialect), is a reference to the morphological similarity of this species with F. fusconotata and also to F. puxcu and F. fusconotata ’s overlapping geographic distribution.
Type material examined. Holotype male, Argentina: Mendoza: Las Heras, Reserva Villavicencio (32 º 31 ’15,5’’S; 69 º0’28, 9’’W); 1680 m. Paratypes: 9 males, same data as holotype. IADIZA.
Distribution. The species is only known from the type-locality.
Diagnosis: Small yellow and grey species very similar to F. fusconotata and F. benjamini. Frontal vitta at narrowest point reduced to a thin line. Eyes bare. Parafacial bare. Antennae light brown. Palpi brownish yellow. Thorax grey-brown, thin brown vittae visible in full length of acr and between dc and ia, but not present at base of scutellum. Two strong pra near spal. T 2 constricted in basal half. F 3 lacking preapical posteroventral protuberance.T 3 lacking medial row of ad. Wings clear. Halteres yellowish-white. Abdomen heart-shaped, greybrown in ground colour, heavily yellow pruinose on laterals of tergites 2–4.
Male: body length 3.1–3.4 mm
Head. Frontal vitta black to silvery, at narrowest point reduced to a thin line. Fronto-orbital plate heavily silvery grey pruinose, at uppermost pair of fr 2 x width of anterior ocellus. Six to seven fr, slightly shorter than flagellum. Eyes bare, antero-internal facets 2 x diameter of remaining; pocl of uniform length as opposed to having a long followed by a short seta. Face and parafacial silvery grey; parafacial at base of flagellum 0.6 x width of same and bare. Facial carina dark grey. Genae grey. Scape light brown, pedicel and flagellum brownish yellow; flagellum short and broad 1.2 to 1.7 x as long as broad, heavily silvery grey pruinose. Arista light brown at base, and short pubescent. Palpi brownish yellow, slightly spatulated, the apex 2 x width of base. Lower oral margin, slightly concave and grooveless.
Thorax: Scutum grey, thin brown vittae visible in full length of acr and between dc and ia, but not present at base of scutellum; pleura grey; 3 + 3 acr, 1 pair of prescutellar acrs; 2 + 3 dc; pprn lacking setulae; 2 strong pra near spal; prealar area bare; 2 prepm, lacking surrounding setulae.
Legs: Coxae brown, trochanters yellow, femora brown; tibiae completely yellow, tarsi dark-brown to black. F 1 normal (length/width = 5); 1 row of pd as long as femoral width; 2 rows of p as long as femoral width; 1 row of pv short in apical fourth but 4 to 6 longer pv at apex. T 1 with 1 subapical pd; 1 apical v and pv; 1 submedial and 1 apical ad. Fore tarsomere 1 0.3 x length of fore tibia, tarsomeres 4 and 5 as wide as long. F 2 with 1 row of weak ad; 2 rows of short a, one in full length and other in medial 1 / 3; with 1 row of av sparse at base, denser and shorter at apex; 2 rows of pv, upper row as long as femoral width and lower short at base, longer at apex; 1 row of p longer and ventrally directed at apex. T 2 constricted in basal half. Ventral pubescence sparse, as long as 0.5 x femoral width; 1 submedial and 3 apical a; 1 subapical ad; 1 strong apical av -v; 1 submedial and 1 apical pd; 1 apical pv and p. C 3 bare at apex of posterior margin. F 3 normal (length/width = 5.5), lacking preapical posteroventral protuberance; 1 row of ad longer and ventrally directed towards apex; 1 row of long and hair- like av, and 2 preapical av longer than femoral width; with a row of very short setulose pv (Fig. 2). T 3 with 1 submedial and 1 subapical d; 1 submedial and 1 apical ad, lacking medial row; 2 to 3 medial and 1 apical short av; apex of ventral and posteroventral surface with a weak ctenidium.
Wings: Clear. Lower calypter oval, upper rounded, both white. Knob of halteres yellowish-white, light brown at base.
Abdomen: Heart-shaped, tergite 2 over 2 x width of tergite 4. Grey-brown in ground colour, heavily yellow pruinose on laterals of tergites 2–4. Hypopygium not protruding.
Postabdomen: Posterior margin of sternite 5 profoundly indented and covered with setae (Fig. 3). Hypandrial arms directed outwards and expanded at apex; postgonites inconspicuous; aedeagus membranous (Fig. 4). Epandrium slightly broadened at posterior margin; cercal plate fused, slightly bilobated at base; bacilliform process cork-screw shaped; surstily long and simple, marginal respect to epandrium (Figs. 5, 6).
Female (unknown).